<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>边框</title>
</head>
<style>
  .box{
    width: 600px;
    height: 400px;
    border: 30px solid transparent;
    border-image: url("../../img/border.png") 30 round;
  }
  .triangle{
    width: 0px;
    height: 0px;
    border-bottom: 100px solid red;
    border-right: 100px solid transparent;
    /*border-left: 100px solid transparent;*/
  }
</style>
<body>
<div class="box"></div>
<div class="triangle"></div>
</body>
</html>